For the manufacture of cast parts, there is conventionally provided a casting mould having a moulding cavity forming the cast part to be manufactured. The molten metal is then cast out from a melt container into the moulding cavity. The melt container can, for example, be a casting furnace or another container which is filled with melt and in which the melt is kept at a temperature level required for casting. Once the melt in the casting mould has solidified to form the cast part to be manufactured, the casting mould and casting part are separated from each other.
The properties of a cast part are influenced markedly by the course of the solidification of the melt in the casting mould and the backfeed required to compensate for the shrinkage in volume. A particularly uniform distribution of properties is thus displayed if the mould is filled with melt in a continuous process, avoiding comparatively large streams of melt in the casting mould, and the solidification starts distributed uniformly and on the side of the casting mould opposing the feeder.
For this purpose, methods are known in which the melt is conveyed into the casting mould counter to the direction in which gravity acts. In some of these casting methods, referred to by specialists as “rising casting”, the melt container is arranged below the casting mould. The melt is then pressed into the moulding cavity of the casting mould via a riser pipe by subjecting to pressure the atmosphere impinging above the melt in the melt container. This generally takes place in that a pressurised gas is introduced into the melt container chamber remaining free of melt. Alternatively, for conveying the melt, low pressure can also be applied to the moulding cavity of the casting mould or the molten metal can be conveyed into the casting mould using electromagnetic forces.
This filling of the casting mould with melt counter to the direction of gravity has the advantage that a steady and controlled casting course is achieved with minimised turbulence of the melt. The risk of casting errors in the cast part manufactured can thus be greatly reduced. However, methods of this type have the drawback that the casting moulds have in each case to dwell in the casting plant for a long period of time required for complete solidification of the cast part formed in each case therein.
A device for carrying out rising casting is known, for example, from DE 100 33 904 A1. In the case of this known device, there is arranged between the casting mould and the melt container a slide closure formed from two plates which are located one on top of the other, are displaceable relative to each other and each have a through-opening. For filling the casting mould, the through-openings are made to overlap, so melt can flow from the melt container into the casting mould through a riser pipe. As soon as the casting mould is filled, one of the slide plates is displaced relative to the other, so the through-openings are closed. The casting mould can then be dispatched and a further casting cycle started.
As soon as a plug of solidified melt has formed in the filling opening in the casting mould, the slide closure can be removed for use. In order to shorten the waiting time preceding this stage, there can be provided on the filling opening a cooling means causing targeted cooling of the melt present in the filling region.
For further improving the quality of cast products, it has been proposed to rotate the casting mould for filling with melt. For this purpose, DE 100 19 309 A1 has proposed linking the upwardly oriented opening in a melt container containing molten metal to a downward pointing filling opening in a casting mould. The casting mould is then rotated, in conjunction with the melt container firmly connected thereto, through approx. 180°. During the course of the rotation, the melt passes from the melt container into the casting mould. Once the end position of the rotation has been reached, the melt container is removed from the casting mould. The hot residual melt, now located on top, in the feeder region can then continue to remain active, under the effect of gravity, and compensate particularly effectively for the loss in volume accompanying the solidification of the melt.
The rotation of the casting mould with the melt container allows the casting mould to be filled completely with molten metal. The fact that the molten metal introduced into the casting mould is exposed to gravity uniformly during the rotation of the mould ensures that the melt passes, on rotation, into all regions of the moulding cavity of the casting mould forming the cast part to be cast. In addition, this casting method, also referred to by specialists as “rotational casting”, optimises the structural constitution on account of directed solidification caused by the orientation of the casting mould accompanying the rotation, thus allowing the manufacture of high-quality cast parts of complex geometric construction.
However, in the case of the known method, the filling of the mould is not optimal if, for example, cylindrical internal geometries require particularly homogeneous solidification morphologies.
In addition to the prior art described hereinbefore, DE 196 49 014 A1 also discloses a method and a device for manufacturing cast parts made of aluminium alloys. Provision is made in this case, for increasing productivity, for the molten aluminium to be pressed upward at a comparatively low pressure into a casting mould made of a gasifiable foam via a riser pipe. After casting-out, the casting mould is rotated, together with the casting container, about an axis of rotation extending substantially horizontally in the region of advance of the cast part.